Acoustic tree and wooden member imaging apparatus

ABSTRACT

An ultrasonic computed tomography tree or log scanner has a plurality of ultrasonic transceivers carried on a belt ( 102 ) sized to encircle a tree ( 100 ). The belt includes an apparatus for engaging is tightly around the tree ( 104 ). The transceivers are strapped around the tree, and their mutual relative distances are known. Electronic circuitry energizes the transmitters in a known sequence. The signals received at each of the receivers are also collected and analyzed. Computed tomographic techniques analyze the time of arrival of the acoustic pulse that is first to arrive at each receiver. A signal processor generates a two-dimensional image of a slice of the tree ( 110 ) at the locus of the belt.

This application is based on and claims priority to U.S. Prov. App. No.60/076,139, filed on Feb. 27, 1998.

BACKGROUND

This invention relates to the non-destructive analysis of standing andfelled trees and poles, such as utility poles, and more particularly togenerating two and three dimensional images of such trees that indicatetheir internal structure.

Trees and utility poles, such as telephone poles, are subject to variouskinds of interior deteriorating and rotting conditions that are notevident from indicia outside of the tree or pole. Trees can undergo suchinternal rot for years, without noticeable symptoms to the leaves, barkor other observable structures. However, once the tree is cut down, andsawn up for use as lumber, paper, veneer, etc., the presence of largeareas of rot greatly diminish the useability of the tree. In addition torot, the presence of other internal structures, such as voids and knots,affects the uses to which a particular tree or tree section can be put.Thus there are many reasons to know the internal structure or conditionof both standing and recently felled trees.

Owners and prospective purchasers of tracts of trees desire to know thegeneral condition of the trees before they are purchased, or beforeefforts are made to log any significant percentage of such trees.Similarly, prospective purchasers of individual trees would like to beable to assess their condition before purchase. Arborists, or thoseresponsible for the health of forests and trees would like to be able toassess the spread of any transmissible disorder of such trees, in orderto better stem the movement of any such condition through a forest.Arborists are also interested in the type of rotting conditionexperienced by the tree, which may indicate the cause and treatment.Different types of rot are evidenced by different patterns of decay.Environmentalists who are interested in maintaining dead trees standing,such as for habitation by spotted owls and other animals, will be ableto identify trees that are not worth logging, which may then be savedfrom logging because the lumber company would have no interest infelling a rotten tree.

Persons with militant anti-lumber attitudes have also been known todrive stainless steel spikes randomly into stands of trees. If such aspike is encountered by a saw during the felling or processing of such atree, it can cause significant damage to equipment and injury topersons. The spikes can not be located by magnetic techniques, becausestainless steel is not magnetically attractive.

At the level of an individual tree, if a lumber mill operator knows ofthe location inside a felled tree where there are rotting conditions, itis possible to make better use of the tree. For instance, if one were toknow that the center of a tree is rotted, with the outside being in goodshape, that tree could be dispatched to a veneer mill, which would“peel” the outer, high quality wood from the tree, stopping when therotted inner section is reached. In addition to rot, it is also helpfulto know the locations of other internal non-uniformities, such as knotsand voids, when sorting logs, or orienting logs for various milloperations. Such triage could be performed on whole trees, or onsections of trees.

Many of the foreging operations must be performed in the field onstanding trees, far from any roads or mills. Thus, any equipment that isrequired to perform such operations must be small enough and lightenough so that it can be carried to the standing tree by a single user.Further, it must be operable under battery or other portable powersources for a length of time that is long enough to make its use worththe effort of transporting it to the site.

Many problems similar to the foregoing also exist with standing woodenpoles, such as utility poles, including telephone poles. Once in placeand tied into a network, it is very expensive to remove and replacethem. However, such poles do suffer from deterioration, such as rot andbug infestation, and must be replaced from time to time. Other types ofwooden members that require knowledge about their internal conditioninclude piers, pilings and scaffolds. These poles and wooden members arealso often far from roads or are not readily accessible to heavymachinery.

Accordingly, for the foregoing reasons, there is a need for a relativelysmall, lightweight, long life apparatus that can generate a twodimensional image of the interior of a standing tree or pole or recentlyfelled tree. There is also need for such a device that would operatequickly enough to give the operator an essentially immediate image ofthe tree or pole under inspection so that decisions of disposition ofthe tree or pole can be made in the field. There is further a need for adevice that can readily be attached and removed from a tree or pole, toprovide an image at different locations along a tree or pole , andfurther, for a device that can generate a three-dimensionalrepresentation of a standing tree or pole or recently felled tree in thefield.

SUMMARY

A preferred embodiment of the apparatus according to the invention is anultrasonic computed tomography tree, pole, or log scanner. A pluralityof ultrasonic transceivers (each of which can both transmit and receiveultrasonic impulses) are carried on a belt that is sized to encircle atypical tree or pole of the size to be examined. The belt includes acinch or chain or other mechanical apparatus for engaging it verytightly around the circumference of the tree or pole to be examined. Thetransceivers are spaced around the tree or pole, and their mutualrelative distances are known. Electronic circuitry is provided forenergizing the transmitters in a known sequence. The signals that arereceived at each of the receivers are also collected and analyzed. Usingcomputed tomographic techniques to analyze the time of arrival of theacoustic pulse that is first to arrive at each receiver, a signalprocessor generates a two dimensional image of a slice surface of thetree or pole at the locus of the belt. In addition to the time ofarrival of the first wave to arrive, the attenuation of the energy ofthe first arriving wave also provides additional information that can beused in conjunction with the images that are based on the arrival time.The signal processing and transceiver controlling are performed byportable, lap-top type computers or smaller computing devices, such asPDAs, such as the Palm Pilot™, sold by 3Com.

The transceivers may include spike-like engaging portions, that arepressed strongly into the bark of the tree to ensure good acousticcoupling. A radar apparatus is also optionally provided to help todetermine the diameter of trees whose cross-sections diverge greatlyfrom circular. The transceivers may be coupled to the signal processorover an infra-red channel. The battery power supply for the apparatusmay be carried by the belt, or it may be separate.

According to another preferred embodiment of the invention, at leasttwo, and preferably three belts, each belt carrying a plurality oftransceivers, as discussed above, are spaced longitudinally along thesection of tree or pole, for instance one to three feet apart from eachother. In such an arrangement, again, pulses from individualtransmitters are received at each of the receivers, and, based oncomputed tomographic analysis, the internal condition of the volumetricportion of the tree is determined over all three spatial dimensions.

Another preferred embodiment of the method of the invention is a methodfor the non-destructive examination of trees, poles, and logs, whichincludes the steps of acoustically coupling a plurality of ultrasonictransceivers to a tree or pole. The transmitters are pulsed according toa known order, and the signals from each transmitter are received ateach of the receivers. The time of reception and the attenuation fromthe original signal is noted for each receiver. Using the time ofarrival information, a two dimensional image is generated, by applyingcomputed tomographic procedures to the data. The two dimensional imageis displayed on a human perceptible device. In addition to the time ofarrival data, the attenuation data may also be used to create anindependent image or enhance the image of the internal structure of thetree, pole, or log. A similar method is conducted for the threedimensional data embodiment of the invention discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims and accompanying drawings, where:

FIG. 1 is a schematic view of an embodiment of an apparatus of theinvention, with a transceiver belt engaged around a tree, and a userholding a computer terminal that houses signal processing components ofthe invention;

FIG. 2 is a schematic view of a transceiver belt of the invention, asshown in FIG. 1, not engaged with a tree or other wooden member;

FIG. 3 shows schematically, in cross section, a plurality oftransceivers, one acting as a source transmitter, the others asreceivers, positioned around a tree, along with indications of the pathsalong which ultrasound pulses may travel;

FIG. 4 is a schematic view of an embodiment of an apparatus of theinvention, with three transceiver belts, as shown in FIG. 2, engagedaround a tree, for generating a three-dimensional image of the internalstructure of the tree;

FIGS. 5A-5L show graphically for each transceiver, the signal that isreceived at all eleven other transceivers, when the transceiver inquestion acts as the source, sending a pulse through a healthy log froma tree;

FIGS. 6A-6L show graphically for each transceiver, the signal that isreceived at all eleven other transceivers, when the transceiver inquestion acts as the source, sending a pulse through a rotten log from atree;

FIG. 7 is a schematic representation of a photograph of a log cut from atree, showing a type of rotting condition that results in large voids;

FIG. 8 is a schematic representation of a photograph of a log cut from atree showing a type of rotting condition that does not result in largevoids;

FIG. 9 is a graphical representation of a computed tomographic twodimensional image of the internal structure of a tree, as is generatedby an embodiment of the apparatus of the invention.

DETAILED DESCRIPTION

A preferred embodiment of the present invention is shown schematicallywith reference to FIG. 1. A transducer belt 102 is secured around astanding tree 100. The belt is secured by a clamping device 104, partlyobscured by the tree. A portable, hand held control unit 106 is shownschematically being held by a user, both from the front and the back. Ona display screen 108, the control unit displays a two dimensional image110 of a cross-sectional slice surface of the tree 100, as generated bythe apparatus of the invention.

The invention can also be used on other wooden members, such as felledtrees, logs, and even large sections of sawn logs. It can also be usedon standing poles, such as utility poles including telephone poles,piers, dock supports, pilings and scaffolding. However, for simplicity,only the use with standing trees will be discussed herein, but it willbe understood that the other uses just mentioned are also contemplated.In the few circumstances where it matters whether the subject ofobservation is a standing tree, a utility pole, or a felled tree or log,etc., that is explicitly mentioned. If not mentioned, it should beassumed that the apparatus described can be used on the other woodenmembers listed, in essentially the same manner.

The transducer belt 102 is shown in more detail with reference to FIG.2, where a belt is shown apart from a tree or log to be examined. Thebelt includes a tightening apparatus 104, which, in this case is shownas having a hook 114 and link 116 that are tightened by a lever 118.This tightening arrangement may be similar to that used by an automobileoil filter wrench. The belt carries along its length a plurality ofspaced apart ultrasonic transducers 112 a, 112 b, 112 c, 112 d, . . .112 n, which are each a combination transmitting and receivingtransceiver. Also carried on the belt is a radar pulse unit 122 andreceive unit 124, whose function is discussed below, and a battery pack120 to power the transceivers and radar units.

The belt may also optionally include an infra-red (IR) band datatransmitter 126, which communicates to the control unit through an IRreceiver 128. The IR transmitter and receiver are each transmitting andreceiving transceivers, for two way communication between the transducerbelt and the control unit.

Each of the transceivers includes a spike-like tooth 130, to help couplethe ultrasonic energy from the transceiver into and out of the tree.Depending on the type of bark and transducer, other shapes, such asshown at teeth 132 and 134 may be used. In some cases, it is beneficialto use a coupling agent, such as petroleum jelly, to couple the energy.In such a case, the cup like tooth 134 may be more effective. Choice ofthe appropriate tooth may be routinely made by the designer. Theultrasonic waves of interest are compressional waves that aretransmitted through the body of the tree.

A typical arrangement of the transceivers is shown with reference toFIG. 3, which is a schematic cross-sectional view of a belt, engagedwith a tree. A plurality of twenty-two transceivers, (R) are arrangedaround a tree. At the moment shown, the transceiver identified as S isacting as the source of ultrasonic energy, and the others, identified asR, are all acting as receivers. At the next moment, the transceiverlocated clockwise one step from the S transceiver may become the source.The paths of acoustic pulses are indicated by the arrows. These paths donot follow straight lines, particularly near the irregularity I.

The mode of operation of the apparatus of the invention is understoodwith reference to FIGS. 5A-5L. Each figure shows eleven traces. Eachtrace represents the signal received at one of the eleven transceivers,which do not include the transceiver that acted as the transmitter. Thesignal has been launched from a single transceiver, acting as atransmitter.

For instance, FIG. 5A shows the situation with respect to a signal thatwas launched from a transmitter that was positioned between thosetransceivers whose reception is shown on the traces numbered 1 and 11,which indicate relatively early arrival of the pulse. The transceiver atlocation number 6 appears to experience arrival of the first pulse aftermost, if not all of the other transceivers.

As shown in FIG. 5A, the time of arrival of the first pulse received bythe transceiver at position number 11 is about 0.03 ms; at position 10at 0.1 ms; at position 9 at 0.13 ms; at position 6 at 0.15 ms, and atposition 2 at 0.07 ms. FIG. 5C shows the situation with the transceiverbetween positions number 1 and 2 being the source. Consequently,transceivers that are closer to this location indicate the earliestarrival of the first wave to arrive. Since the time of transmission isknown, the time of arrival is also indicative of time of flight (“TOF”).As used herein, time of arrival and TOF are used interchangeably, eventhough they are not precisely the same.

The transceiver controller steps through each of the transceivers,activating each successive one to be the transmitter for a designatedset of measurements. While one transceiver is transmitting, the othersare all receiving, and the signals received at each are recorded. Aftereach of the transceivers has functioned as a transmitter, the controllerstops causing the transceivers to be energized. (For certain operations,it may be beneficial to step through each of the transceivers a secondtime, causing them each to act as a transmitter a second time around thecircuit.)

Thus, from the data shown in FIGS. 5A-5L, the TOF of an ultrasound pulsethrough the tree can be determined. Each pulse transmission andreception pair provides a record of the path of shortest durationthrough the tree. That does not mean that it is the shortest path, froma geometrical, straight line standpoint. This is because sound wavestravel all throughout the tree, and the wave that arrives first willhave made its way along a path of tree elements (analogous to pixels ona CRT) that permit the fastest travel of sound therethrough. Forinstance, a tree element that is entirely void will exhibit a soundtransmission characteristic similar to that of air. A tree element thatis healthy will transmit sound therethrough at a higher velocity. Thus,an ultrasonic pulse that has travelled through a void may take longer toarrive than one that travelled a longer distance, skirting the border ofthe void.

FIGS. 6A-6L show similar data as FIGS. 5A-5L, but for a tree thatincludes some rot.

By applying computed tomographic (“CT”) techniques to all of the time offirst arrival data from each transmitter location to each receiverlocation, it is possible to generate a two dimensional image of theslice of the tree around which the transceivers are mounted, which imagedifferentiates among different tree elements based on their acoustictransmission properties, showing the tree graded by transmissionvelocity.

This transmission velocity bears a direct relationship to properties ofthe tree, such as its density, incompressibility and rigidity, whichproperties can be correlated to properties that are of interest to thelogging, arborial, maintenance, safety and environmental interestsoutlined above, such as rot, knots, voids and embedded metal spikes.

The tomographic techniques and methods that are applied to the TOF dataare similar to those that are used in x-ray tomography. They are alsosimilar to those that were described in work of one of the inventorsherein, Matarese, Joseph R., NONLINEAR TRAVELTIME TOMOGRAPHY, a thesissubmitted to the Department of Earth, Atmospheric, and PlanetarySciences in partial fulfillment of the requirements for the degree ofDoctor of Philosophy in Geophysics, in 1993, the entire disclosure ofwhich is incorporated herein fully by reference.

The Matarese thesis concentrates on using computed tomography (CT) toanalyze geological formations, such as the geological conditions aroundoil wells, and the like. However, with geological formations, it is verydifficult to surround the subject with locations of transceivers. To doso requires drilling a well of the desired depth at every location whereit is desired to locate a transceiver. In the Matarese thesis, such anarrangement of transceivers is referred to as a “Medical Survey” becauseof the analogy to medical CT where x-ray transceivers are located allaround the patient's body.

Chapters 2, 3 and 4 of the Matarese thesis are of particular interest.Chapter 2 discusses Modeling Traveltimes and Raypaths, focussing on:first arrival traveltimes, traveltime measurement; traveltime modelling,including both ray-based and Eikonal Methods, of which ray shooting andtwo-point perturbation are examples of the former and finite difference,graph-theoretical and extrapolation are examples of the latter. Chapter2 also discusses Tomographic traveltime modeling, including homogeneous,smoothly-varying, layered and rough models. Chapter 3 discussesreconstructing velocities from traveltimes, particularly the tomographyproblem, linearized inversion and nonlinear inversion. It is principallythe techniques that are outlined in this Ch. 3, that are applied to thetime-of-flight data, to reconstruct the velocities at different treeelement locations from the traveltimes.

Chapter 4 provides a nonlinear programming approach to traveltimeinversion, including raytracing, backprojection, regularization, steplength calculation, adding prior information, a numerical solution ofthe linearized problem, preconditioning, optimization and convergence,and parallel implementation.

It is helpful to have some foreknowledge of the velocity to be expectedin the majority of tree elements. However, it is not necessary to havethis foreknowledge. If it is available, however, it reduces the numberof computational iterations that must be conducted to converge upon aresult with certainty. Typically, about 20-30 iterations of thecomputations are required.

A schematic rendition of an acoustic tomographic image is shown in FIG.9. Regions (L) of the tree with lower velocity are differentiated on thecontroller monitor by color (or shading) from those (H) having highervelocity properties.

It has been found that suitable results can be achieved by usingultrasound pulses in the frequency range of from 15 kHz to 200 kHz,preferably less than 100 kHz. The low end of this range may not bestrictly considered to be ultrasound in some circumstances, being withinthe range of human hearing. However, it is a suitable range for thepractice of the present invention. In particular, to detect rottedconditions, it is thought to be important to use relatively lowerfrequency radiation. The power should be enough to ensure that theultrasonic energy is transmitted all the way through the tree. However,because the device should be portable and lightweight, it is desireablenot to use excessively powerful pulses, because that would result in theuse of heavier batteries than is necessary.

It has been found that the moisture content of the wooden member bearsupon the power requirements. Generally speaking, moister members, suchas standing or recently felled trees, require lower power than do driermembers, such as seasoned lumber and utility poles.

The processor should be fast enough and powerful enough such that it cangenerate an image from twelve sensors in about thirty seconds. Each treeelement pixel would be on the order of one square inch in area. This isachievable with technology available in 1998 laptop computers. It isalso believed to be possible to be achievable with even smallercomputing devices, such as those known as personal digital assistants,or “PDAs”, of which the Palm III™, sold by 3Com, is a representativetype. In some cases, the PDA may need additional memory, over itsstandard complement.

It is also possible to analyze waves that arrive after the firstarrivals (which later waves typically include surface waves) to identifythe location of any object (such as metal spikes) that is near thesurface. These are waves, such as shown in FIGS. 5A-5L, that arriveafter the first few waves to arrive.

ENERGY ATTENUATION

The foregoing discussion has focussed on generating two dimensionalimages that correspond to the velocity characteristics of the differentelements of the tree. It is also beneficial to take into account theenergy attenuation characteristics of the different tree elements. Thiscan also be done with computed tomography techniques. It will beobserved that the traces shown in FIGS. 5A-L and 6A-L show not only thetime of arrival of the first wave to arrive at each transceiver, butalso the amplitude of each such first arriving wave. With knowledge ofthe amplitude of the transmitted pulse, the attenuation of each firstarriving wave can be determined.

Using the same types of calculations and techniques as were used tocompute the velocity characteristics of the tree elements, the energyattenuating properties of the tree elements can also be determined. Itis most convenient to conduct the energy attenuation analysis after thevelocity analysis, because the velocity analysis identifies the pathsthat the first arriving pulses actually follow. Knowing these paths, thetree elements that are responsible for the various degrees of energyattenuation can be identified.

It is believed that the effect of tree condition on energy attenuationis more severe than the effect of tree condition on velocity variation.Thus, the image that is derived at least in part from the velocityattenuation analysis is believed to provide a more sensitive, anddetailed image. It is possible to generate an image based only on theattenuation information, or on a combination of the attenuation and thevelocity information.

CHARACTERISTICS OF THE BELT

The belt 102 that carries the transceivers, battery power supply and theother components should satisfy several criteria. It should be able tobe tightened to a significant degree. This can be accomplished by manydifferent types of clamping apparati, such as a levered hook, similar toan oil filter wrench; a small motor that cinches the strap tight; ahydraulic cylinder. During tightening, the belt should not stretch. Thisis because it is important, for purposes of the tomographic techniques,to know with precision the distance between transceivers. Thus, it isbeneficial to construct the belt from a lightweight, stretch resistantmaterial, such as Kevlar™ brand fibers (sold by Du Pont) or carbonfibers. Kevlar™ brand and carbon fibers also have the advantage of beinglightweight and very strong.

The belt should also not transmit ultrasonic vibration through itself,but rather should damp out the transmission of any such vibration. Thisis to insure that the vibration received by the transceivers hastraveled through the tree, rather than around the tree, through thebelt. Any such “cross-talk” would be undesireable. Thus, the belt caninclude vibration damping links in between the transceiver links.

The belt also typically carries a plurality of radar pulse generators122 and radar receivers 124. (Only one of each is shown. Thesecomponents would be equally spaced around the perimeter of the tree.)These are used to determine the true diameter of the tree, in the casethat the tree perimeter is not circular. The radar operation is bytransmission, not reflection.

THREE DIMENSIONAL IMAGE

The foregoing discussion has described an apparatus that generates animage of a two-dimensional slice surface of a tree. FIG. 4 shows anapparatus that generates a three-dimensional image of a block of tree,for instance six feet in length. This embodiment employs three (or more)belts 102, 202 and 302, each substantially identical to the belt 102that is discussed above. The operation is essentially the same, exceptthat the process traverses through using each of the transceivers oneach of the three belts as a transmitter. For each momentarytransmitter, the first signal to arrive is noted at each of the othertransceivers in the belt in which the transmitter resides, and, in theother two (or more) belts.

The same computed tomography techniques that are set forth in theMatarese thesis that were mentioned above in connection with the twodimensional embodiment can be applied in the three dimensional case withonly a little more complexity due to the additional transceivers, andthe added geometrical dimension. The result of these techniques is athree dimensional image 210 of a cylindrical portion of the tree, eachlevel of which can be imaged as a two-dimensional slice. Such a threedimensional image can be rotated around any axis to view from any angle,and can be sliced for a two dimensional image by any plane, as is commonwith current computer aided design and medical imaging packages

Thus, a three dimensional image may be garnered. This embodiment may beparticularly useful for orienting logs during mill operation, and alsofor locating embedded objects, such as spikes inserted by those seekingto limit logging activity. This is because the spikes are relativelysmall, and the scope of examination is expanded by quite a bit whenthree belts are used. When one belt is used, a slice of tree on theorder of a few inches thick is examined. When three belts are used, aslice on the order of four to six feet thick can be examined. Thus, byincreasing the weight of the apparatus by three, its field ofexamination is increased on the order of twenty fold.

The invention may be used with very large trees, such as Sitka spruce,Douglas firs, and redwoods, which may be as large as ten feet indiameter.

The foregoing discussion should be understood as illustrative and shouldnot be considered to be limiting in any sense. While this invention hasbeen particularly shown and described with references to preferredembodiments thereof, it will be understood by those skilled in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the invention as defined by theclaims.

In particular, the invention can also be used to examine all types ofwooden members, such as utility poles, including telephone poles, piers,dock supports, scaffolding, and pilings.

The corresponding structures, materials, acts and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or acts for performing the functions incombination with other claimed elements as specifically claimed.

Having described the invention, what is claimed is:
 1. An ultrasoundapparatus for determining the internal condition of a wooden member,said apparatus comprising: a. a belt, sized to encircle a wooden memberto be examined, which belt carries: i. a plurality of ultrasonictransceivers, spaced along said belt; and ii. a tightening mechanismthat enables said belt to be tightened around said wooden member; b. acontroller configured to: i. energize selected of said transceivers totransmit ultrasound energy, and others of said transceivers to receivesaid ultrasound energy; ii. receive signals that are based on saidtransmitted energy and said received energy; and iii. analyze saidreceived signals to generate a signal that corresponds to the conditionof a two dimensional slice surface of said wooden member; and c. asignal channel that couples said transceivers to said controller.
 2. Theultrasound apparatus of claim 1, said controller configured to identifyat each receiving transceiver, a first signal to arrive that has beentransmitted from a given transmitting transceiver, and to identify thetime of arrival of said first signal to arrive, and, based on analyzingsaid times of arrival of said first signal to arrive at each receivingtransceiver, generating said signal that corresponds to the condition ofsaid two dimensional slice surface of said wooden member.
 3. Theultrasound apparatus of claim 1, said controller configured to compare,at each receiving transceiver, an amplitude of a first signal to arrivethat has been transmitted from a given transmitting transceiver, with anamplitude of a corresponding signal that has been transmitted by saidgiven transmitting transceiver, and, based on analyzing said comparisonof amplitudes, and any attenuation therebetween, generating said signalthat corresponds to the condition of said two dimensional slice surfaceof said wooden member.
 4. The ultrasound apparatus of claim 2, saidcontroller configured to compare, at each receiving transceiver, anamplitude of said first signal to arrive that has been transmitted froma given transmitting transceiver, with an amplitude of a correspondingsignal that has been transmitted by said given transmitting transceiver,and, based on analyzing said comparison of amplitudes, and anyattenuation therebetween, as well as said times of arrival of said firstsignal to arrive, generating said signal that corresponds to thecondition of said two dimensional slice of said wooden member.
 5. Theultrasound apparatus of claim 1, said transceivers each comprising amember engagement tooth, designed to couple acoustic energy between saidtransceiver and a wooden member.
 6. The ultrasound apparatus of claim 5,said tooth comprising a spike.
 7. The ultrasound apparatus of claim 5,said tooth comprising a cup.
 8. The ultrasound apparatus of claim 1,further comprising, carried upon said belt, at least one radartransmitter and a paired radar receiver, and means for coupling saidradar transmitter and receiver to said controller, said controllerfurther being configured to analyze signals received at said radarreceiver to determine the relative positions of said ultrasoundtransceivers.
 9. The ultrasound apparatus of claim 1, said controllerconfigured to apply computer aided tomographic (CAT) techniques toanalyze said received signals to generate said signal that correspondsto the condition of a two dimensional slice surface of said woodenmember.
 10. The ultrasound apparatus of claim 1, said signal channelthat couples said transceivers to said controller comprising aninfra-red frequency band channel.
 11. The ultrasound apparatus of claim1, said plurality of transceivers numbering at least ten.
 12. Theultrasound apparatus of claim 1, further comprising: a. a second belt,sized to encircle said wooden member to be examined, which second beltcarries: i. a second plurality of ultrasonic transceivers, spaced alongsaid belt; and ii. a tightening mechanism that enables said belt to betightened around said wooden member; b. a signal channel that couplessaid second plurality of transceivers to said controller; and c. saidcontroller further being configured to: i. energize said secondplurality of transceivers to receive said ultrasound energy transmittedby said selected transceivers of said first plurality; ii. energizeselected of said second plurality of transceivers to transmit ultrasoundenergy, and others of said second plurality of transceivers to receivesaid ultrasound energy transmitted by selected of said second pluralityof transceivers; iii. energize said first plurality of transceivers toreceive said ultrasound energy transmitted by said selected transceiversof said second plurality; iv. receive signals that are based on saidtransmitted energy and said received energy at said second plurality oftransceivers; and v. analyze said received signals from said first andsecond plurality of transceivers to generate a signal that correspondsto the condition of a three dimensional volume of said wooden member.13. The ultrasound apparatus of claim 12, further comprising: a. a thirdbelt, sized to encircle said wooden member to be examined, which thirdbelt carries: i. a third plurality of ultrasonic transceivers, spacedalong said belt; and ii. a tightening mechanism that enables said thirdbelt to be tightened around said wooden member; b. a signal channel thatcouples said third plurality of transceivers to said controller; and c.said controller further being configured to: i. energize said thirdplurality of transceivers to receive said ultrasound energy transmittedby said selected transceivers of said first and second pluralities; ii.energize selected of said third plurality of transceivers to transmitultrasound energy, and others of said third plurality of transceivers toreceive said ultrasound energy transmitted by selected of said thirdplurality of transceivers; iii. energize said first and secondpluralities of transceivers to receive said ultrasound energytransmitted by said selected transceivers of said third plurality; iv.receive signals that are based on said transmitted energy and saidreceived energy at said third plurality of transceivers; and v. analyzesaid received signals from said first and second and third pluralitiesof transceivers to generate a signal that corresponds to the conditionof a three dimensional volume of said wooden member.
 14. The ultrasoundapparatus of claim 1, said belt comprising a material that does notstretch under the tension required to secure it to a wooden member andacoustically couple said transceivers to said wooden member.
 15. Theultrasound apparatus of claim 14, said belt comprising fibers selectedfrom the group consisting of Kevlar™ and carbon.
 16. The ultrasoundapparatus of claim 1, further comprising a battery unit, carried by saidbelt, which battery unit provides power to said transceivers.
 17. Theultrasound apparatus of claim 1, said belt sized to encircle a tree. 18.The ultrasound apparatus of claim 1, said belt sized to encircle autility pole.
 19. The ultrasound apparatus of claim 1, furthercomprising a device that generates a human perceptible signal thatcorresponds to the condition of a two dimensional slice surface of saidwooden member.
 20. The ultrasound apparatus of claim 1, said beltcomprising acoustic energy attenuation material, that impedes thetransmission of acoustic energy from any transceiver, through said belt,to any other transceiver.
 21. A method for determining the internalcondition of a wooden member, said method comprising the steps of: a.acoustically coupling a first plurality of ultrasonic transceivers to awooden member, around its circumference, said transceivers carried by aremovable belt; b. causing each of said transceivers, in a known order,to generate acoustic energy that is coupled into said wooden member, andthat is received by each other of said transceivers; c. transmitting, toa control unit, signals that correspond to said received acousticenergy; d. in said control unit, determining, for each transmittingtransceiver, times of arrival at each receiving transceiver of the firstacoustic pulse to arrive; and e. based on said times of arrival,generating a signal that corresponds to the condition of a twodimensional slice surface of said wooden member.
 22. The method of claim21, said step of generating a signal comprising the step of usingcomputer aided tomographic techniques to generate said signal thatcorresponds to the condition of a two dimensional slice surface of saidwooden member.
 23. The method of claim 22, further comprising the stepsof: a. in said control unit, determining, for each transmitter,amplitude attenuation at each receiver of the first acoustic pulse toarrive; and b. based on said attenuation and said time of arrival,generating a signal that corresponds to the condition of a twodimensional slice surface of said wooden member.
 24. The method of claim21, further comprising the step of displaying on a human perceptibledisplay, said signal that corresponds to the condition of a twodimensional slice surface of said wooden member.
 25. The method of claim21, further comprising: a. acoustically coupling a second plurality ofultrasonic transceivers to said wooden member, around its circumference,said second plurality of transceivers carried by a second removablebelt; b. causing each of said second plurality of transceivers toreceive said acoustic energy that has been transmitted by said firstplurality of transceivers; c. causing each of said second plurality oftransceivers, in a known order, to generate acoustic energy that iscoupled into said wooden member, and that is received by each other ofsaid second plurality of transceivers; d. causing each of said firstplurality of transceivers to receive said acoustic energy that has beentransmitted by said second plurality of transceivers; e. transmitting,to said control unit, signals that correspond to said received acousticenergy, received at said first and said second plurality oftransceivers; f. in said control unit, determining, for eachtransmitting transceiver, times of arrival at each receiving transceiverof the first acoustic pulse to arrive; and g. based said times ofarrival, generating a signal that corresponds to the condition of athree dimensional volume of said wooden member.
 26. The method of claim21, further comprising the step of transmitting radar signals from afirst location on said belt, and receiving said radar signals at asecond location on said belt, and using said received radar signals todetermine the relative positions of said ultrasound transceivers. 27.The method of claim 21, said step of coupling a first plurality ofultrasonic transceivers to a wooden member comprising the step ofcoupling said transceivers to a standing tree.
 28. The method of claim21, said step of coupling a first plurality of ultrasonic transceiversto a wooden member comprising the step of coupling said transceivers toa felled tree.
 29. The method of claim 21, said step of coupling a firstplurality of ultrasonic transceivers to a wooden member comprising thestep of coupling said transceivers to a utility pole.
 30. The method ofclaim 25, said step of generating a signal comprising the step of usingcomputer aided tomographic techniques to generate said signal thatcorresponds to the condition of a three dimensional volume of saidwooden member.
 31. A method for determining the internal condition of awooden member, said method comprising the steps of: a. acousticallycoupling a first plurality of ultrasonic transceivers to a woodenmember, around its circumference, said transceivers carried by aremovable belt; b. causing each of said transceivers, in a known order,to generate acoustic energy that is coupled into said wooden member, andthat is received by each other of said transceivers; c. transmitting, toa control unit, signals that correspond to said received acousticenergy; d. in said control unit, identifying, for each transmittingtransceiver, a feature of acoustic energy arrival at each receivingtransceiver; and e. based on said feature, generating a signal thatcorresponds to the condition of a two dimensional slice surface of saidwooden member.